Fluid Geochemistry of High-Temperature Hydrothermal Fields in the Okinawa Trough

Kawagucci, Shinsuke

doi:10.1007/978-4-431-54865-2_30

Cited by 28 publications

(42 citation statements)

References 77 publications

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“…Gas chemistry of the Solitaire fluid showed typical compositional and isotopic features, as found in the sediment‐starved basalt‐hosted MOR hydrothermal systems. The highest concentrations of CO 2 , H 2 , and CH 4 in the Solitaire samples were 16.2 m m , 0.46 m m , and 0.047 m m , respectively (Figs and and Table ) (Kawagucci and references therein; Konn et al . ).…”

Section: Resultsmentioning

confidence: 95%

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Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

et al. 2016

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Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion (489 mm), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 μm and Mn = 78 μm). Chloride depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than ~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with an off‐spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalt‐hosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the spreading axis, was characterized by high H2 concentration of 2.7 mm. The H2 enrichment was likely attributable to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents. Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced the H2 enrichment. The quantitative cultivation test revealed that the microbial community associated with the hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around the H2‐enriched hydrothermal fluid flows was also inferred from the 13C‐ and D‐depleted signature of CH4 in the collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013.

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Section: Resultsmentioning

confidence: 95%

“…Vertical bars show empirically representative ranges of H 2 concentration for silicic, mafic, and ultramafic‐hosted hydrothermal systems. This is updated from the diagram in Kawagucci () with Konn et al . ().…”

Section: Resultsmentioning

confidence: 99%

Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

et al. 2016

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“…Heterotrophic activity was determined based on the potential activity of the anaerobic oxidation of acetate. The incubations were conducted at 30 and 60°C based on the in situ temperatures in Supplementary Figure S1 C-and D-depleted methane in the high-temperature hydrothermal fluids (Kawagucci, 2015). The concurrent isotopic changes in methane (ΔδD CH4 /Δδ 13 C CH4 ) in the shallow low-temperature zones fell into a range bracketed by slopes of 7-19 (Figure 2), which have been reported to be representative values for microbial methane oxidation (Alperin et al, 1988;Kessler et al, 2006;Holler et al, 2009;Feisthauer et al, 2011).…”

Section: Geochemical Evidence Of Hydrothermal Fluid Input and Methanementioning

confidence: 98%

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor

et al. 2016

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Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the MidOkinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ 13 C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to~45°C. However, in the past, higher temperatures of 106-198°C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

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“…In the Iheya North knoll hydrothermal field, concentrations of K + , Ca 2+ , and B 3+ in anomalous layer in hydrothermal plume water columns are higher than in average seawater [4,50] (Figures 5 and 6) and are lower or higher than in hydrothermal fluids (K + 6.9-82 mmol kg −1 ; Ca 2+ 0-25 mmol kg −1 ; B 3+ 0.44-2.27 mmol kg −1 ; SO 4 2− −7-15 mmol kg −1 ) in the area [9,60], and those of Mg 2+ and SO 4 2− are lower than in average seawater [4,50] (Figure 7). The Ca/SO 4 2− ratios in the anomalous layers are higher, and the Mg 2+ /Ca 2+ ratios are lower than in average seawater [50,60,61] (Figure 8), suggesting that they result from active hydrothermal discharge (e.g., [1,2,62]). …”

Section: Variable Major Components In Hydrothermal Plumementioning

confidence: 99%

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

et al. 2018

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Studies of the major components of hydrothermal plumes in seafloor hydrothermal fields are critical for an improved understanding of biogeochemical cycles and the large-scale distribution of elements in the submarine environment. The composition of major components in hydrothermal plume water column samples from 25 stations has been investigated in the middle and southern Okinawa Trough. The physical and chemical properties of hydrothermal plume water in the Okinawa Trough have been affected by input of the Kuroshio current, and its influence on hydrothermal plume water from the southern Okinawa Trough to the middle Okinawa Trough is reduced. The anomalous layers of seawater in the hydrothermal plume water columns have higher K + , Ca 2+ , Mn 2+ , B 3+ , Ca 2+ /SO 4 2− , and Mn 2+ /Mg 2+ ratios and higher optical anomalies than other layers. The Mg 2+ , SO 4 2− , Mg 2+ /Ca 2+ , and SO 4 2− /Mn 2+ ratios of the anomalous layers are lower than other layers in the hydrothermal plume water columns and are consistent with concentrations in hydrothermal vent fluids in the Okinawa Trough. This suggests that the chemical variations of hydrothermal plumes in the Tangyin hydrothermal field, like other hydrothermal fields, result in the discharge of high K + , Ca 2+ , and B 3+ and low Mg 2+ and SO 4 2− fluid. Furthermore, element ratios (e.g., Sr 2+ /Ca 2+ , Ca 2+ /Cl − ) in hydrothermal plume water columns were found to be similar to those in average seawater, indicating that Sr 2+ /Ca 2+ and Ca 2+ /Cl − ratios of hydrothermal plumes might be useful proxies for chemical properties of seawater. The hydrothermal K + , Ca 2+ , Mn 2+ , and B 3+ flux to seawater in the Okinawa Trough is about 2.62-873, 1.04-326, 1.30-76.4, and 0.293-34.7 × 10 6 kg per year, respectively. The heat flux is about 0.159-1,973 × 10 5 W, which means that roughly 0.0006% of ocean heat is supplied by seafloor hydrothermal plumes in the Okinawa Trough.

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Fluid Geochemistry of High-Temperature Hydrothermal Fields in the Okinawa Trough

Cited by 28 publications

References 77 publications

Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

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